Generally, in an interior permanent magnet synchronous motor (IPMSM), a permanent magnet is inserted into a rotator. The interior permanent magnet synchronous motor has characteristics suitable for being used in a motor of a hybrid electric vehicle because it has good durability and good drivability at high speeds. In addition, the interior permanent magnet synchronous motor has a reluctance torque so that a large output can be obtained, and also has nonlinear parameters.
In such an interior permanent magnet synchronous motor, a motor current is determined such that a compound torque, made up of a general electromagnetic torque and a reluctance torque, is maximized.
In addition, in the interior permanent magnet synchronous motor, flux weakening control is needed to obtain good output characteristics and drivability at high speeds. A precise torque control is also needed under nonlinear parameter conditions.
In a prior permanent magnet synchronous motor control method, a control is performed based on a model of a motor. That is, a current applying angle θ for an operation with a maximum torque is calculated. Furthermore, a control, in a type of flux weakening feedback loop or magnetic flux command feedforward, is performed for the flux weakening control. However, because errors in calculation result due to the nonlinearity of the parameters, performance of the motor becomes erratic and preciseness of control deteriorates.
Further, the calculates amount for the control is excessive, so it is difficult to realize such control. Furthermore, in prior control methods based on the motor model, it is difficult to consider characteristics of the permanent magnet synchronous motor, thereby making it difficult to obtain maximum torque operation and uniform flux weakening operation performance.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.